The present applicant proposes in Patent Literature 1 and Patent Literature 2 such a configuration of an insulating container that an exterior sleeve is slidably fit onto an outer circumferential surface of a body portion of a container main body and one end of the exterior sleeve is bonded onto the outer circumferential surface of the body portion as well as the exterior sleeve is compressed in an up-and-down direction to have a plurality of slit forming sections provided on the exterior sleeve project outwardly from the exterior sleeve to form an insulating holder, the insulating container characterized in that the exterior sleeve is pulled-up and pulled-down with a help of a human power to deform the slit forming sections into the insulating holder. The insulating container disclosed in the above described publications has produced a reasonable effect.
On the other hand, Patent Literature 3 discloses a heat-insulating developing tacky adhesive label with a heat-shrinkable film. However, the label has such a configuration that a deformation caused by heat-shrinkage is controlled by a cut line having a transverse H-shape and therefore the configuration has a drawback that it is only applicable to labels.
It is an object of the present invention, as a result of a continued study, to provide an insulating container in which a slit forming section is deformed into an insulating holder by using a heat-shrinkable film which is directly heated or a shrinkable film which is indirectly heated by microwave.    Patent Literature 1: Japanese Patent Laid-open Publication No. 2006-44723    Patent Literature 2: Japanese Patent Laid-open Publication No. 2006-160346    Patent Literature 3: Japanese Patent Laid-open Publication No. 2007-137468